It is known to blend a compound of the formula (1-1) into a polymer, for improving the processing stability of the polymer such as polybutadiene and the like (see, e.g., patent documents 1 and 2).
    (Patent document 1) JP-A No. 1-168643 (Production Example 1)    (Patent document 2) JP-A No. 4-264051 (Example 1)